1. Field of the Invention
The present invention relates to a solid-state scanning-type optical writing device. The present invention specifically relates to a solid-state scanningtype optical writing device for writing an image (latent image) on a photosensitive member by ON/OFF switching of light based on image data using an optical shutter element of PLZT.
2. Description of the Related Art
In general, various optical writing devices have been proposed which control the ON/OFF switching of single pixels using an optical shutter element of PLZT or the like to form an image (latent image) on an image carrying member such as printing paper used as a silver salt-sensitive member, or film or photosensitive member used for electrophotography. In such optical writing devices of the full color type, light exposure of a surface of a photosensitive member is accomplished by ON/OFF switching of an applied voltage to an optical shutter element to switch colors by high-speed rotation of a filter which separates the light into the three primary colors of red (R), green (G), and blue (B).
As shown in FIG. 8, transmission light intensity of the various colors red (R), green G), and blue (B) of the optical shutter element have different characteristics depending on the voltage applied to the optical shutter element. Transmission light intensity is a value obtained by dividing the exit light intensity from the optical shutter element by the entrance light intensity. As can be readily understood from FIG. 8, the optimum drive voltage (referred to as the half-wave voltage) is referred to as Rv (about 35.5 V) for red (R) light (wavelength: 650 nm), Gv (about 33 V) for green (G) light (wavelength: 550 nm), and Bv (about 29 V) for blue (B) light (wavelength: 450 nm). That is, there is a difference of several volts relative to the optimum drive voltage among the various colors.
In order to prevent irregular density of each color when switching the drive voltage of the optical shutter element to the optimum value for each color, pulse-like high-speed switching of a high voltage is necessary. There is a possibility, therefore, that high-voltage spike noise will be generated during switching. Spike noise, as is well known, is a phenomenon occurring when the response speed of a circuit changing a voltage is unable to track the change in voltage so as to cause a momentary excessive voltage. There is concern that the driver integrated circuit (IC) for the optical shutter element may be damaged when spike noise is generated.